1. Field of the Invention
The present invention relates to a sputtering target made of a platinum-cobalt alloy which is excellent in workability in hot working operation, and a method specifically adapted to manufacture the same.
2. Prior Art
Due to the rapid progress of information processors in recent years, a recording capability of higher density is required for magnetic disk units which constitute the main parts of a memory storage. A thin film of a chromium-platinum-cobalt (Cr-Pt-Co) alloy has been hitherto known as being suitable for effecting such high-density recording since it contains a large amount of platinum and exhibits high coercivity. A conventional Cr-Pt-Co alloy target which consists, for example, of 5 to 20% by weight of Cr, 10 to 55% by weight of Pt and balance Co may be suitably sputtered to form magnetic recording thin films.
However, the aforesaid conventional target has a high magnetic permeability .mu. of about 30 to 40. Therefore, when forming a thin film by the application of a magnetron sputtering process, the rate of formation of the thin film cannot be increased. In addition, since thin targets can only be employed, the target must frequently be exchanged for a new one, resulting in hindrances to industrial application. Furthermore, the surface of the target is locally subjected to erosion during the sputtering, so that the efficiency of use of the target is deteriorated.
Moreover, although the platinum contained in a large amount in the target alloy enhances coercivity, it makes the resulting target susceptible to cracking when subjected to plastic working, whether hot working or cold working. Therefore, it is very difficult to manufacture targets of a large area.
Furthermore, when the aforesaid target is produced by a known casting method, there occur casting defects which may often induce abnormal discharge during the sputtering operation or may cause foreign matter to adhere to the film formed.